Heretofore, in the art of stone cutting with a wire saw, the cutting wire has been intermittently fed down against the stone either by a clock feed, a mechanical ratchet feed, or an electronic variable speed down feed motor. The disadvantage of all of these prior art methods is that none of them could be optimized for the conditions that existed in each stone cutting wire, and no direct feedback from the wire was possible. As a result, in the prior art, the stone cutting or sawing operation was frequently carried out in a slow, inefficient and uneconomical manner, without the proper degree of bow and cutting pressure being constantly maintained on the wire of the saw mechanism.
The sole purpose of this invention is to completely cure the above deficiency of the prior art by providing an automatic feedback control for the down feed of the cutting or sawing wire. An almost exactly constant cutting pressure is thus maintained on the wire at all times as well as the proper degree of bow in the wire to assure cutting of the stone with maximum efficiency and economy.
The automatic feedback control of the invention constantly measures the bow in the cutting wire and adjusts the downfeed accordingly. No other prior art devices can accomplish this. While the "bow" may be measured or sensed mechanically, optically or by pneumatic means, electronic sensing means is the least subject to wear and malfunction and therefore is employed in the invention.